Plastic Warriors has an article on modeling camouflage netting. The key ingredients in this project are fine gauze and super glue.
Modeling
Making German East Africa Buildings
Major Thomas Foolery has a photo tutorial on making WWI era German East Africa administrative buildings.
The finished product is quite impressive.
Modeling Tall Grasses
Here’s a photo tutorial on modeling tall grasses, using old brushes.
It looks like you’d be able to get quite a bit of material out of one of those cheap house painting brushes.
Modeling Troy For Skirmish Gaming
While not quite a tutorial, 15mm Wargaming for Fun and Sanity has a great article on modeling a mud brick / adobe town. The build was designed for ancient Troy, but as the author notes, such buildings are extremely versatile, applicable to more periods than you can count — even science fiction.
I’m inspired.